Singleton birthweight by gestational age following in vitro fertilization in the United States

Establishing the Most Accurate Due Date in Dichorionic Twin Gestations by First and Second Trimester Ultrasound

OBJECTIVE

To determine the optimal sonographic dating of dichorionic gestations.

MATERIALS AND METHODS

We reviewed dichorionic pregnancies conceived with assisted reproductive technologies (ART) at 2 institutions between 2006-2016, excluding fetuses with major anomalies. Gestational age was calculated with smaller, larger, and mean of the crown-rump lengths (CRL) and biometry midgestation and compared to the ART age. The mean and mean absolute deviation of the observed gestational age from the ART age was calculated to assess accuracy, precision, and presence of bias. The incidence of small for gestational age using the smaller and larger CRLs was compared to the ART age via McNemar's test.

RESULTS

Based on 140 ultrasounds, the CRL from the smaller twin best approximates the true gestational age with least bias compared to the larger twin or average (mean absolute deviation: 2.8, mean deviation: -0.1 [95% CI: -0.4, 0.2] versus 2.7, -0.9 [-1.1, -0.6] and 2.9, -1.5 [-1.8, -1.3], in days, respectively). Based on 165 ultrasounds, biometry from the smaller fetus is least accurate compared to the larger or mean (11.8, 2.5 [1.5, 3.6] versus 11.7, 0.8 [-0.3, 1.8] and 11.9, -1.0 [-2.0, 0.04], respectively). The incidence of small for gestational age neonates did not differ from the true rate using either the CRL from the larger or smaller twin (p > .05).

CONCLUSION

In ART dichorionic gestations, ultrasound of the smaller fetus is most accurate in establishing gestational age in the first trimester but least accurate in the second, though all methods performed well with little clinical difference.

Associations of IVF singleton birthweight and gestation with clinical treatment and laboratory factors: a multicentre cohort study

STUDY QUESTION

Do IVF treatment and laboratory factors affect singleton birthweight (BW)?

SUMMARY ANSWER

BWs of IVF-conceived singleton babies are increasing with time, but we cannot identify the specific treatment factors responsible.

WHAT IS KNOWN ALREADY

IVF-conceived singleton babies from fresh transfers have slightly lower BW than those conceived naturally, whilst those from frozen embryo transfer (FET) cycles are heavier and comparable to naturally conceived offspring. Our recent studies have shown that BW varies significantly between different IVF centres, and in a single centre, is also increasing with time, without a corresponding change in BWs of naturally conceived infants. Although it is likely that factors in the IVF treatment cycle, such as hormonal stimulation or embryo laboratory culture conditions, are associated with BW differences, our previous study designs were not able to confirm this.

STUDY DESIGN, SIZE, DURATION

Data relating to BW outcomes, IVF treatment and laboratory parameters were collated from pre-existing electronic records in five participating centres for all singleton babies conceived between August 2007 and December 2014.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Seven thousand, five hundred and eighty-eight births, 6207 from fresh and 1381 from FET. Infants with severe congenital abnormalities were excluded. The primary outcome of gestation-adjusted BW and secondary outcomes of unadjusted BW and gestation were analysed using multivariable regression models with robust standard errors to allow for the correlation between infants with the same mother. The models tested treatment factors allowing for confounding by centre, time and patient characteristics. A similar matched analysis of a subgroup of 379 sibling pairs was also performed.

MAIN RESULTS AND THE ROLE OF CHANCE

No significant associations of birth outcomes with IVF embryo culture parameters were seen independent of clinic or time, including embryo culture medium, incubator type or oxygen level, although small differences cannot be ruled out. We did not detect any significant differences associated with hormonal stimulation in fresh cycles or hormonal synchronization in FET cycles. Gestation-adjusted BW increased by 13.4 (95% CI 0.6-26.1) g per year over the period of the study, and babies born following FET were 92 (95% CI 57-128) g heavier on average than those from the fresh transfer.

LIMITATIONS, REASONS FOR CAUTION

Although no specific relationships have been identified independent of clinic and time, the confidence intervals remain large and do not exclude clinically relevant effect sizes. As this is an observational study, residual confounding may still be present.

WIDER IMPLICATIONS OF THE FINDINGS

This study demonstrates the potential for large scale analysis of routine data to address critical questions concerning the long-term implications of IVF treatment, in accordance with the Developmental Origins of Health and Disease hypothesis. However, much larger studies, at a national scale with sufficiently detailed data, are required to identify the treatment parameters associated with differences in BW or other relevant outcomes.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the EU FP7 project grant, EpiHealthNet (FP7-PEOPLE-2012-ITN-317146). No competing interests were identified.

TRIAL REGISTRATION NUMBER

N/A.

The impact of IVF on birthweight from 1991 to 2015: a cross-sectional study

STUDY QUESTION

Has birthweight (BW) changed over time among IVF-conceived singletons?

SUMMARY ANSWER

Singleton BW has increased markedly over the past 25 years.

WHAT IS KNOWN ALREADY

IVF conceived singletons have had a higher incidence of low BW compared to spontaneously conceived singletons, and this has raised concerns over long-term increased risks of cardio-metabolic disease. However, few causal links between IVF procedures and BW have been robustly established, and few studies have examined whether BW has changed over time as IVF techniques have developed.

STUDY DESIGN, SIZE, DURATION

A total of 2780 live born singletons conceived via IVF or ICSI treated in the reproductive medicine department of a single publicly funded tertiary care centre between 1991 and 2015 were included in this retrospective study. The primary outcome measure was singleton BW adjusted for gestational age, maternal parity and child gender. Multivariable linear regression models were used to estimate the associations between patient prognostic factors and IVF treatment procedures with adjusted BW.

PARTICIPANTS/MATERIALS, SETTING, METHODS

All singletons conceived at the centre following IVF/ICSI using the mother's own oocytes, and non-donated fresh or frozen/thawed embryos with complete electronic data records, were investigated. Available electronic records were retrieved from the Human Fertilization and Embryology Authority for dataset collation. Multiple linear regression analysis was used to evaluate associations between IVF treatment parameters and BW, after adjusting for the year of treatment and patient characteristics and pregnancy factors.

MAIN RESULTS AND THE ROLE OF CHANCE

In the primary multivariable model, singleton BW increased by 7.4 g per year (95% CI: 3.2-11.6 g, P = 0.001), an increase of close to 180 g throughout the 25-year period after accounting for gestational age, maternal parity, child gender, IVF treatment parameters, patient prognostic characteristics and pregnancy factors. Fresh and frozen embryo transfer-conceived singletons showed a similar increase in BW. Frozen/thawed embryo transfer conceived singletons were on average 53 g heavier than their fresh embryo conceived counterparts (95% CI: 3.7-103.3 g, P = 0.035).

LIMITATIONS, REASONS FOR CAUTION

The independent variables included in the study were limited to those that have been consistently recorded and stored electronically over the past two decades.

WIDER IMPLICATIONS OF THE FINDINGS

There has been a progressive BW increase in IVF singletons over time in one large centre with consistent treatment eligibility criteria. Such a change is not seen in the general population of live born singletons in the UK or other developed countries, and seems to be specific to this IVF population. This may be a reflection of changes in practice such as undisturbed extended embryo culture to the blastocyst stage, optimized commercial culture media composition, single embryo transfer and ICSI. Moreover, singletons conceived from frozen/thawed embryos had higher birth weights when compared to their fresh embryo transfer counterparts. The causal pathway is unknown; however, it could be due to the impact on embryos of the freeze/thaw process, self-selection of embryos from couples who produce a surplus of embryos, and/or embryo replacement into a more receptive maternal environment.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the EU FP7 project grant, EpiHealthNet (FP7-PEOPLE-2012-ITN-317146). The authors have no competing interests to declare.

TRIAL REGISTRATION NUMBER

N/A.

Maternal and neonatal outcomes associated with infertility

Objective: To investigate perinatal outcomes in a cohort of fertile and infertile nulliparous women. Design: Retrospective cohort study. Setting: Academic medical center. Patients: All nulliparous women delivering singletons ≥24-week gestation at our center from 1 January 2012 to 31 December 2012 were included. Women were classified into two groups - fertile and infertile - based on a chart review at the time of delivery. Outcome measure: Perinatal outcomes of interest included mode of delivery, gestational age at delivery, and birth weight. Results: A total of 3293 mother/infant dyads fulfilled the inclusion criteria. Of these, 277 women (8.4%) were classified as infertile. Infertile women were significantly older than fertile women. In bivariate analyses, infertile women were more likely to undergo cesarean delivery (51.8 versus 36.1%, p < .001) and deliver at an earlier gestational age (38.9 ± 2.3 versus 39.4 ± 1.7 weeks, p < .0001). Infertility was no longer significantly associated with cesarean delivery after adjusting for maternal age. Infertility remained associated with an earlier gestational age at delivery after adjusting for maternal age and maternal race (β coefficient -0.42, 95%CI -0.64, -0.2). There was no difference in infant birth weight. Late preterm deliveries (34-36 completed gestational weeks) accounted for 8.3% of deliveries for infertile women compared to 4.3% for fertile women (p = .032). Conclusions: We conclude that the increased risk of cesarean section associated with infertility is driven by maternal age. Late preterm infants represent a key cohort for further evaluation in the perinatal outcomes of infertile women.

Peripartum and postpartum outcomes in uncomplicated term pregnancy following ART: a retrospective cohort study from two Italian obstetric units

STUDY QUESTION

Do singleton uncomplicated term pregnancies conceived by assisted reproductive technology (ART) have adverse peripartum and postpartum outcomes?

SUMMARY ANSWER

Term pregnancies following ART, even if uncomplicated until birth, have a higher risk of retained placenta and postpartum hemorrhage (PPH).

WHAT IS KNOWN ALREADY

There is consistent evidence that pregnancies following ART have higher incidence of complications during pregnancy. However, few studies specifically investigated birth outcomes in ART term pregnancies.

STUDY DESIGN, SIZE, DURATION

A retrospective cohort study was conducted on 14 415 deliveries at two university tertiary care obstetric units. Clinical data were extracted by reviewing obstetric records of all deliveries from 1 January 2010 to 31 December 2014, in a standardized electronic database regarding the mother’s health before and during pregnancy, complications during pregnancy and at birth, and neonatal outcome.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Following an accurate evaluation of exclusion criteria (multiparity, maternal pre-pregnancy diseases, prior uterine surgery, fetal malformations, intrauterine deaths, elective cesarean section and pregnancy complications), the group of uncomplicated singleton term pregnancies from autologous ART conception by in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) (n = 188) was compared with a maternal age and body mass index (BMI) matched group of spontaneous pregnancies (n = 1168). Cases of intrauterine insemination (IUI) (n = 14) and ovulation induction with timed intercourse (n = 18) were not included. Labor, delivery and postpartum outcomes were evaluated. Odds ratios (OR) were adjusted with multivariable logistic regression to maternal age, BMI, nationality and gestational age at birth.

MAIN RESULTS AND THE ROLE OF CHANCE

The age of women in the final analysis ranged from 25 to 45 years, while BMI ranged from 17 to 34 kg/m². Uncomplicated term pregnancies with ART conception had a higher risk of operative delivery (adjusted OR 1.40, 95% confidence interval (CI) 1.01–1.95), retained placenta (adjusted OR 2.63, 95% CI 1.31–5.26) and PPH (adjusted OR 2.86 95% CI 1.37–5.99). Conversely, ART conception did not increase the risk of induced labor (adjusted OR 1.18, 95% CI 0.85–1.65). However, patients that conceived by ART and underwent labor induction had a higher risk of failed induction compared with the control group (adjusted OR 2.53, 95% CI 1.23–5.21). Infants born after ART had a similar birthweight, Apgar score and arterial blood pH compared with spontaneously-conceived ones.

LIMITATIONS, REASONS FOR CAUTION

The database lacked specific information about causes of infertility, smoking habit, family income and details on ART (fresh versus frozen cycle, IVF versus ICSI), limiting, in part, our analysis of the results. However, only autologous IVF/ICSI pregnancies were included in order to prevent bias related to conception by oocyte/embryo donation. In vivo conception ART cases were excluded because they were too few to allow comparison with IVF/ICSI. Nevertheless, the inclusion of only uncomplicated pregnancies provides a highly homogeneous and still representative population sample. Study sample is representative of a well-resourced obstetric facility in a high-income country, limiting to some extent the generalizability of study results.

WIDER IMPLICATIONS OF THE FINDINGS

Pregnancies conceived by autologous ART that proceed uncomplicated until term may require counseling about the risk of placental retention with PPH.

STUDY FUNDING/COMPETING INTERESTS

The authors have no conflict of interest and funding to declare.

Birthweight in infants conceived through in vitro fertilization following blastocyst or cleavage-stage embryo transfer: a national registry study

PURPOSE

In vitro fertilization (IVF) infants have lower birthweights than their peers, predisposing them to long-term health consequences. Blastocyst transfer (BT), at day 5-6 post-fertilization, is increasing in usage, partially due to improved pregnancy outcomes over cleavage-stage transfer (CT, day 2-3). Data to date, however, have been inconclusive regarding BT's effects on birthweight.

METHODS

Participants included all US autologous, single-gestation, fresh embryo transfer cycles initiated from 2007 to 2014 that resulted in a term infant (N = 124,154) from the National Assisted Reproductive Technology Surveillance System. Generalized linear models including obstetric history, maternal demographics, and infant sex and gestational age were used to compare birthweight outcomes for infants born following BT (N = 67,169) with infants born following CT (N = 56,985) and to test for an interaction between transfer stage and single embryo transfer (SET).

RESULTS

Infants born following BT were 6 g larger than those born following CT (p = 0.04), but rates of macrosomia (RR 1.00, 95% CI 0.96-1.04) and low birthweight (LBW, RR 1.00, 95% CI 0.93-1.06) were not different between the groups. The interaction between SET and transfer stage was significant (p = 0.02). Among SET infants, BT was associated with 19.26 g increased birthweight compared to CT (p = 0.008).

CONCLUSIONS

The increase in birthweights identified following BT is unlikely to be clinically relevant, as there were no differences in rates of macrosomia or LBW. These findings are clinically reassuring and indicate that the increasing use of BT is unlikely to further decrease the on average lower birthweights seen in IVF infants compared to their naturally conceived peers.

Individualized growth assessment: conceptual framework and practical implementation for the evaluation of fetal growth and neonatal growth outcome

Fetal growth abnormalities can pose significant consequences on perinatal morbidity and mortality of nonanomalous fetuses. The most widely accepted definition of fetal growth restriction is an estimated fetal weight less than the 10th percentile for gestational age according to population-based criteria. However, these criteria do not account for the growth potential of an individual fetus, nor do they effectively separate constitutionally small fetuses from ones that are malnourished. Furthermore, conventional approaches typically evaluate estimated fetal weight at a single time point, rather than using serial scans, to evaluate growth. This article provides a conceptual framework for the individualized growth assessment of a fetus/neonate based on measuring second-trimester growth velocity of fetal size parameters to estimate growth potential. These estimates specify size models that generate individualized third-trimester size trajectories and predict birth characteristics. Comparisons of measured and predicted values are used to separate normally growing fetuses from those with growth abnormalities. This can be accomplished with individual anatomical parameters or sets of parameters. A practical and freely available software (Individualized Growth Assessment Program) has been developed to allow implementation of this approach for clinical and research purposes.

Birthweights and Down syndrome in neonates that were delivered after frozen-thawed embryo transfer: The 2007-2012 Japan Society of Obstetrics and Gynecology National Registry data in Japan

Aim

To evaluate the use of frozen embryos on the outcome of assisted reproductive technology (ART), a retrospective study of the Japanese Assisted Reproductive Technology Registry data during the years 2007-2012 was conducted.

Methods

A total of 124 946 singleton neonates who reached term gestation following ART from 2007-2012, with 80 660 achieved through frozen-thawed embryo transfer (ET) and 44 286 being achieved through fresh ET, were analyzed for their birthweights and chromosomal abnormalities.

Results

The birthweight of the neonates from the frozen-thawed ETs was significantly higher than that of those from the fresh ETs throughout all the study years. The frequency of Down syndrome was 0.17% for the fresh ETs and 0.13% for the frozen-thawed ETs in the period 2007-2012. This study showed that frozen-thawed ETs result in a constant increase of the average birthweight between 37 and 41 weeks gestational age and lower frequencies of Down syndrome.

Conclusion

Frozen-thawed ETs were comparable to the fresh ET method, with the exceptions of higher birthweights and a lower frequency of Down syndrome in the neonates that were born from frozen-thawed ET. The increase in birthweights was not proportional to the gestational ages. This cannot be explained with any well-known mechanism. The frequency of chromosomal abnormalities needs detailed data for analysis.